Method for treating a screw-cement retained prosthesis and adjustment for a screw-cement retained prosthesis

ABSTRACT

A method for treating a screw-cement retained prosthesis and an abutment are disclosed. The method for treating the screw-cement retained prosthesis comprises the steps of implanting a fixture in an alveolar bone; engaging an abutment including a first screw hole to the fixture using a screw; providing a prosthetic appliance including a second screw hole formed correspondingly to the first screw hole; and bonding the prosthetic appliance and the abutment by interposing dental cement between the abutment and the prosthetic appliance. The present invention includes advantages of a screw retained prosthesis and a cement retained prosthesis and can solve the problems of the screw and cement retained prostheses. Furthermore, in order to easily separate and remount the bonded abutment and prosthetic appliance from the fixture, an allowance groove, which may provide an allowance space, is formed in a receiving portion.

TECHNICAL FIELD

The present invention relates to a method for treating implantprosthesis and an abutment for the prosthesis, in detail to a method fortreating implant prosthesis which is simple to treat and in which theprosthesis is easy to assemble and disassemble and an abutment for theprosthesis which is employed in treatment.

BACKGROUND ART

A dental implant means a dental treating method or an artificial toothstructure that is formed by implanting an artificial dental root in aregion where a tooth has been partially or wholly lost, causing theartificial dental root to adhere to an alveolar bone, and fixing aprosthesis or crown to the artificial dental root. Generally, theimplant comprises a titanium fixture, an abutment fixed onto thefixture, an abutment screw for fixing the abutment to the fixture, and aprosthesis as an artificial tooth secured to the abutment.

The implant makes it possible to treat only an injured portion withoutinjuring adjacent teeth or tissue around the lost teeth, retards anabsorption rate of bone tissue by supporting the bone tissue, and canprovides masticatory force and an aesthetic appearance equal to that ofnatural teeth.

As such, implants have become widely used in dental treatment methodsfor repairing an injured or lost tooth.

Conventional implants are divided into a screw retained prosthesis (SRP)and a cement retained prosthesis (CRP) according to a method fortreating an implant.

Screw Retained Prosthesis (SRP)

The screw retained prosthesis has been used from when implants werefirst developed, and continue to be used today. In the screw retainedprosthesis, fundamentally, a finished prosthetic appliance is fixed toan implant with a screw, and the prosthetic appliance can be easilyremoved or replaced since they are engaged by the screw. There are twotypes in the screw retained prosthesis. One is a type that is treated byintegrally fixing an UCLA abutment and a prosthetic appliance to form aprosthetic assemble, then by mounting the prosthetic appliance directlyto a fie, and the other one is a type that is treated by connecting afixture and a transmucosal abutment, then by mounting a prostheticassemble onto the transmucosal abutment, wherein the prosthetic assembleis formed by fixing an upper abutment (gold cylinder) and a prostheticappliance.

FIG. 1 a is a sectional view of a conventional screw retained prosthesisusing an UCLA abutment.

Referring to FIG. 1 a, a screw retained prosthesis 10 using an UCLAabutment comprises a fixture 12 implanted into an alveolar bone and anabutment 14, which is formed integrally with a prosthetic appliance 18and disposed on the fixture 12. The prosthetic appliance 18 and theabutment 14 are integrally formed on the outside and are formed with ahole through the center.

A screw 16 is tightened through the hole to the fixture 12, so that theprosthetic appliance 18 and abutment 14 are fixed to the fixture 12.

FIG. 1 b is a sectional view of a conventional screw retained prosthesisusing an intermediate abutment.

Referring to FIG. 1 b, the screw retained prosthesis 20 using anintermediate abutment comprises a fixture 22, an intermediate abutment24, and an upper abutment 26, which is formed integrally with aprosthetic appliance 28 and is disposed on the intermediate abutment 24.The intermediate abutment 24 comprises a hole corresponding to a firstscrew 23, wherein the first screw 23 is engaged through the intermediateabutment 24 to the fixture 22, so that the intermediate abutment 24 isfixed to the fixture 22.

A second screw 25 is inserted through a hole that passes through theprosthetic appliance 28 and the upper abutment 26, and the second screw25 is engaged to a screw hole formed on an upper portion of the firstscrew 23, so that the prosthetic appliance 28 and the upper abutment 26are fixed to the intermediate abutment 24.

As shown in FIGS. 1 a and 1 b, ready-made articles such as the UCLAabutment 14 and the upper abutment 26, which are fitted to upperportions of the fixture or the intermediate abutment, are housed withinlower portions of the finished prosthetic appliances 18, 28 and areintegrally formed with the prosthetic appliances when the prostheticappliances are cast.

A major feature of the screw retained prosthesis is that the screw holeis formed in an occlusal surface of the prosthetic appliance so thatengagement between of the screw and the fixture can be adjusted throughthe screw hole. Therefore, the screw retained prosthesis has advantagesas follows:

First, the prosthetic appliance can be easily separated and remounted,even after the prosthetic appliance is completed and mounted in an oralcavity.

The prosthetic appliance is easily repaired and remounted only if theprosthetic appliance is separated from the fixture in cases where repairor replacement of the prosthetic appliance is needed due to accidentalbreakage of the prosthetic appliance, the screw need to be tightenedsince the screw is loosened of itself, a patient undergoes the treatmentand later complains of inconvenience regarding the prosthetic appliancewhich is mounted to the patient, and some of plural implant fixturesfail.

In such cases, the screw retained prosthesis allows the prostheticappliance to be very easily separated. That is to say, the prostheticappliance can be separated without damage by loosening the screw throughthe screw hole and remounted by tightening the screw.

Second, the screw retained prosthesis makes the treatment possible evenwhen the distance between an implant and a tooth that faces the implantis short. For example, the UCLA abutment can only be used if thedistance is 5 mm or greater.

However, the screw retained prosthesis also has serious disadvantagesinstead of satisfying the requisites.

Since the prosthetic appliance should be passively fitted to the fixtureof an understructure, the screw retained prosthesis should bemanufactured precisely up to its near completion. Therefore, the screwretained prosthesis is complicated to manufacture, and excessivemanufacturing time and cost may be required.

Furthermore, if the implant is not completely manufactured and mounted,various stresses can be applied to the implant, so that the excessivestress may often bring about loss of bone around the implant or breakageof the prosthetic appliance or the implant itself.

A problem that often occurs in the screw retained prosthesis is thephenomenon that the screw becomes loose. Some reports say that the screwlooseness occurs in about 25˜30% of the screw retained prosthesis. Thatis to say, compared with a fit implant prosthesis, an unfit implantprosthesis causes the screw to be strained and permanently deformed evenby a small biting force, so that the screw is easily loosened.

In order to solve this problem, the screw retained prosthesis should befixed by passive fit. In order to fabricate the prosthesis with thepassive fit in the oral cavity, first a precise working model should befabricated, and then the prosthesis should be precisely fabricatedthereon.

In order to fabricate the exact precise working model, preciseimpression making, fabrication of the precise working model, andfabrication of the precise prosthetic appliance needs to be performed.However, if contraction, deformation or the like of material isconsidered, such work requires a high degree of expert training. Also,due to features of the fabricating processes, a great deal of time isneeded for treatment and fabrication. Therefore, fabrication as well astreatment costs a great deal, and the cost of materials also increases.Thus, the screw retained prosthesis is very expensive with regard tototal costs.

Cement Retained Prosthesis (CRP)

Contrary to the screw retained prosthesis, the conventional cementretained prosthesis (CRP) is treated by fixing a cement type abutment tothe implant fixture with a screw, disposing a finished prostheticappliance that is separately fabricated onto the fixed abutment, andbonding the prosthetic appliance and the abutment by interposing dentalcement therebetween.

FIG. 2 is a sectional view of the conventional cement retainedprosthesis.

Referring to FIG. 2, the conventional cement retained prosthesis 30comprises a fixture 32, a cement type abutment 34, and a prostheticappliance 38. The abutment 34 formed with a screw hole is disposed ontothe fixture 32 implanted into the alveolar bone, and then is fixed tothe fixture 32 by tightening a screw 36 to the fixture 32 through thescrew hole.

The prosthetic appliance 38 is fitted into the fixed abutment 34, andthen the abutment 34 and the prosthetic appliance 38 are bonded byinterposing dental cement therebetween. Contrary to the screw retainedprosthesis, after manufacturing the prosthetic appliance 38 separatelyfrom the abutment 34, the prosthetic appliance 38 and the abutment 34are bonded with the dental cement.

Therefore, the most major feature in appearance, of the conventionalcement retained prosthesis is that there is not a screw hole in theocclusal surface of the prosthetic appliance. Therefore, contrary to thescrew retained prosthesis, artificial teeth are inconspicuous inappearance, so that the prosthetic appliance can be formed as naturalteeth. However, once the prosthetic appliance is mounted cannot beseparated by loosening a screw.

The cement retained prosthesis solves all the disadvantages of the screwretained type. That is to say, with the cement retained prosthesis, 1)the passive fit between the fixture and the prosthetic appliance can beeasily achieved; 2) as a result, stress applied to the fixture when theprosthetic appliance is connected is reduced; 3) the screw does notoften become loose; 4) clinical procedure and manufacturing processesare simple; 5) time can be saved; and 6) manufacturing costs arereduced.

Most of all, the greatest advantage of the cement retained prosthesis isto simply solve the problems caused from an unfit between the prostheticappliance and the abutment by a space between them and the dental cementinterposed. Contrary to the screw retained type, which requires the highdegree of precision, the cement retained prosthesis is simple in itsimpression and manual operational processes, and achieves the passivefit between the implant and the prosthetic appliance as long as somefundamental rules are kept.

Due to the above reasons, the cement retained type is preferred to thescrew retained type lately.

However, as mentioned above, the cement retained prosthesis has adisadvantage that it is not easy to separate and remount the prostheticappliance. The sole method to separate the prosthetic appliance from theimplant in the cement retained type is to apply an external force. As anexample, in a case of single cement retained prosthesis, the screw maybe come loose. In this case, even if using temporary cement, it isnearly impossible to remove the prosthetic appliance without damage ofthe screw threads or the prosthetic appliance. If a prosthesis comprisesplural implants that are integrally formed, since retaining force causedby the plural implants is increased, it becomes even more impossible toremove the prosthetic appliance.

Another problem of the cement retained prosthesis is that the treatmentis difficult when intermaxillary distance is short. In practice, thereare many cases of the short intermaxillary distance. In this case, ifusing the cement retained type, the length of the abutment becomes shortand due to this retaining force is reduced, so that potential for damageor loss of the prosthetic appliance is increased.

Furthermore, still another problem of the cement retained type is thatit is difficult to completely remove the cement that remains in the oralcavity after bonding the prosthetic appliance with the cement. If theremaining cement is not completely removed, the remaining cement maycause the implant to fail since inflammation occurs at gingiva aroundthe implant over a long period of time.

DISCLOSURE OF INVENTION

As described above, advantages and disadvantages of the screw retainedprosthesis and the cement retained prosthesis are summarized as follows.The screw retained prosthesis has the advantages that the prostheticappliance is freely mounted and separated, and the treatment can beperformed even with a short intermaxillary distance. However, there aresome disadvantages that it is difficult to achieve a precise passivefit, the screw often comes loose, precise clinical and manualoperational procedures are required, and a high cost and a long time arerequired.

Meanwhile, the cement retained type has many advantages of providing aneasy passive fit, simple clinical and manual operational procedures, andtime and cost savings. However, there are some shortcomings as follows:it is difficult to mount and separate disassemble and repair theprosthetic appliance; when the intermaxillary distance is short, illeffects may occur; it is difficult to remove the remaining cement fromthe oral cavity; and it is impossible to polish a border if theprosthetic appliance is not fitted flush to the border.

Therefore, one object of the present invention is to provide a tertiaryprosthetic method, which can adopt and reject the advantages and solvethe shortcomings of both prosthetic methods. That is to say, it is theobject to provide a prosthesis treating method and an abutment whichmake the clinical and manual operation procedures simple; easily providea passive fit with time and cost savings; make a screw hard to loosen;can be applied even in a short intermaxillary distance; make it easy torepair and mend the prosthetic appliance; make it easy to remove theremaining cement of subgingival; make it possible to polish the borderof the prosthetic appliance; and enable the prosthetic appliance to beseparated and remounted without damage whenever required.

Furthermore, another object of the present invention is to provide amethod for treating an implant and an abutment wherein the abutment canbe easily mounted and separated even if axial lines of the fixture andthe abutment do not accord with each other.

According to a preferred embodiment of the present invention forachieving the above described objects, a method for treating thescrew-cement retained prosthesis comprises implanting a fixture in analveolar bone; engaging an abutment including a first screw hole to thefixture using a screw; providing a prosthetic appliance including asecond screw hole formed correspondingly to the first screw hole; andbonding the prosthetic appliance and the abutment by interposing dentalcement between the abutment and the prosthetic appliance.

The present invention has features of the cement retained prosthesis(CRP) since the prosthetic appliance and the abutment are bonded usingthe dental cement, and also has features of the screw retainedprosthesis (SRP) since the screw can be tightened or loosened throughthe first and second screw holes. That is to say, since the abutment istightened to the fixture and the prosthetic appliance is bonded onto theabutment with the cement, the treatment makes the precise passive fitpossible and is quickly and simply performed. Furthermore, since thesecond screw hole is formed in the prosthetic appliance, it is possibleto tighten and loosen the screw, so that the prosthetic appliance can beeasily separated from and remounted to the fixture. Therefore, permanentcement may be used as the dental cement.

The method for treating the implant according to the present invention,which includes the advantages of the screw retained type and the cementretained type and solves the disadvantages of both the types, isreferred to as a screw-cement retained prosthesis or a screw-cementretained implant, hereinafter, an SCRP implant.

Concretely, in the method for treating the SCRP implant, before theprosthetic appliance and the abutment are bonded with the dental cement,the prosthetic appliance is subjected to trial adaptation. The trialadaptation of the prosthetic appliance is the process determiningwhether the prosthetic appliance is fitted to the abutment, so that itis confirmed by assembling the prosthetic appliance and the abutmentwithout dental cement.

Furthermore, before the prosthetic appliance and the abutment arebonded, the first screw hole is filled with supplementary filler such asgauze or cotton ball. As such, the supplementary filler may be used inorder to prevent the first screw hole from being clogged with the dentalcement such as the permanent cement, which is introduced into the firstscrew hole during the bonding process.

Contrary to the cement retained prosthesis (CRP), even after bonding theprosthetic appliance and abutment of the SCRP implant can be easilyseparated from the fixture. Since the prosthetic appliance and abutmentcan be separated by loosening the screw through the second screw hole,the remaining cement after the bonding process can be cleanly removed,and it is also possible to completely finish the implant treatment bypolishing the border of the prosthetic appliance.

According to a preferred embodiment of the present invention forachieving the above described objects, the SCRP abutment, which is akind of an abutment for a cement retained prosthesis used with anexternal fixture, comprises a screw hole formed upward and downwardthrough an abutment body; and a receiving portion for receiving ajoining projection formed on the upper end of the fixture, wherein thereceiving portion comprises a sticking groove stuck to the upper end ofthe joining projection and an allowance groove providing an allowancespace, which causes the joining projection to be easily separated fromand joined to the sticking groove.

Fundamentally, the SCRP abutment according to the present invention hasa structure similar to the abutment used in the cement retainedprosthesis. However, it is a feature the SCRP abutment that it comprisesa receiving portion that is divided into a sticking groove and anallowance groove. As an example application of the SCRP abutment withthe feature of the sticking groove and the allowance groove, in additionto the conventional cement retained abutment, there is a titanium cementretained abutment, a gold cement retained abutment, a gold-plastic UCLAabutment, a plastic UCLA abutment, a temporary abutment, or the like. Animpression coping of transfer copings can be also applied. In addition,all parts, which have features of the present invention and are used byjoining an analogue upper portion for a manual operation and an externalhexagonal-prosthesis, may be applied.

The sticking groove is stuck to a joining portion of the fixture such asthe joining projection when the abutment is connected, so that therelative movement between the abutment and the fixture is limited, andit is possible to set the abutment in a predetermined direction. Thesticking groove is generally formed correspondingly to hexagonalcylindrical shape of an external hexagonal-fixture. Alternatively, thesticking groove is formed in a circle corresponding to the shape of thejoining groove or the joining projection of the fixture. Alternatively,the sticking groove is also formed as a non-circular shape where joiningprojections are formed on a circular cylinder, a polygonal cylinder, ora polygonal pyramid. When the joining projection of the fixture and thesticking groove of the abutment are formed in a non-circle, the abutmentis prevented from rotating on the fixture, and the abutment can beeasily repositioned.

The allowance groove is positioned at the lower portion of the stickinggroove and provides an allowance space between the joining projection ofthe fixture and the receiving portion, so that the joining projectioncan be easily stuck to and separated from the receiving portion.Concretely, the allowance groove is formed with inclination from thelower end of the sticking groove in a conical shape so that entry of thejoining projection can be guided, and is formed in a step shape from thelower end of the sticking groove so that a circular cylindrical orpolygonal cylindrical allowance space with a dimension larger than thatof the sticking groove can be provided.

It is preferable, but not limited to, that the depth of the stickinggroove be between 10%˜80% of the depth of the receiving portion. If theintegrated abutment and prosthetic are easily separated from the fixturewhile relative rotation of the abutment can be prevented, the depth ofthe sticking groove may be formed with a smaller or larger depth thanthat specified above.

The SCRP abutment structure according to the present invention isusefully employed in the case that the plural abutments are integrallybonded to a prosthetic appliance.

For example, when the plural fixtures are implanted into the alveolarbone, the plural fixtures are implanted generally slantingly at certaindegrees of angles with respect to each other.

However, a SCRP prosthetic portion formed using the conventionalhexagonal cement retained abutments does not have a sufficient allowancespace between the abutments and the joining projections of the fixtures.That is to say, when the prosthetic portion is separated from thefixtures, the abutments should be separated in longitudinal directionsto the respective receiving portions. However, since the directions ofthe receiving portions and joining projections do not accord with eachother, the prosthetic portion is not able to separate from the fixture.

However, the SCRP prosthetic portion formed using the abutment accordingto the present invention can be provided with the allowance space by theallowance groove formed in the receiving portion. That is to say, whenthe prosthetic portion is separated from the fixture, the joiningprojection of the fixture frees itself from the sticking groove so thatthe joining projection can move within the predetermined range throughthe allowance groove, and the SCRP prosthetic portion can be separatedfrom the fixture due to the allowance space which the allowance grooveprovides.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 a is a sectional view of a conventional screw retained prosthesisusing an UCLA abutment.

FIG. 1 b is a sectional view of a conventional screw retained prosthesisusing an intermediate abutment.

FIG. 2 is a sectional view of the conventional cement retainedprosthesis.

FIG. 3 is a sectional view of an SCRP implant according to Embodiment 1of the present invention.

FIGS. 4 a to 4 f are sectional views for explaining a method fortreating the SCRP implant according to Embodiment 1.

FIG. 5 a are sectional views for explaining a method for treating theSCRP implant according to Embodiment 2.

FIG. 5 b is a sectional view for explaining a separating process of theSCRP implant according to Embodiment 2.

FIG. 6 is a sectional view of a SCRP prosthesis according to anotherembodiment of the present invention, which is similar to Embodiment 2.

FIG. 7 is a partial sectional view of an SCRP prosthesis for explainingthe example of using an abutment for the SCRP prosthesis according toEmbodiment 3 of the present invention.

FIG. 8 is a bottom partially cutaway perspective view of the abutment ofFIG. 7.

FIG. 9 is a bottom view of the abutment of FIG. 7.

FIG. 10 is a front view for explaining engagement between the abutmentand the fixture according to Embodiment 3.

FIG. 11 is a partial sectional view for explaining the example of usingthe abutment according to Embodiment 3, and shows an example of thetreatment with the two prosthetic appliances integrally formed.

FIG. 12 is a bottom partially cutaway perspective view of an abutmentaccording to Embodiment 4 of the present invention.

FIG. 13 is a front view for explaining the engagement between thefixture and the abutment according to Embodiment 4.

FIG. 14 is a bottom partially cutaway perspective view of an abutmentaccording to Embodiment 5 of the present invention.

FIG. 15 is a bottom partially cutaway perspective view of an abutmentaccording to Embodiment 6 of the present invention.

BEST MODE FOR CARRYING OUR THE INVENTION

Though the embodiments of the present invention will be described asbelow referring to the accompanying drawings, the present invention isnot limited or restricted by the below embodiments.

Embodiment 1

FIG. 3 is a sectional view of an SCRP implant according to Embodiment 1of the present invention, and FIGS. 4 a to 4 f are sectional views forexplaining a method for treating the SCRP implant according toEmbodiment 1.

Referring to FIG. 3, the SCRP implant 100 according to Embodiment 1comprises a fixture 110, an abutment 120, a screw 140 and a prostheticappliance 150.

The fixture 110 comprises the thread 114 formed in its outer surface andis implanted along the thread 114 to the alveolar bone. The thread 114of the implanted fixture 110 is fused with tissue of the alveolar boneand then is fixed to the alveolar bone. Generally, considerable time isneeded for bonding the thread 114 and the alveolar bone to each other.

A hexagonal cylindrical joining projection 112 is formed on the uppersurface of the fixture 110, in which a thread hole corresponding to ascrew 130 is formed along the centerline of the joining projection 112.

An abutment 120 comprises a receiving portion for receiving the joiningprojection 112 and the receiving portion is formed in a hexagonalcylindrical shape, which corresponds to the shape of the joiningprojection 112. A first screw hole 124 is formed on the center of theabutment 120 and the screw 130 is engaged with the fixture 110 throughthe first screw hole 124.

Also, a prosthetic appliance 140 of an SCRP prosthesis 100 comprises asecond screw hole 144. The prosthetic appliance 140 is fabricated of atwo-layered structure of a metal framework and a porcelain or only metalstructure and is formed with the second screw hole 144 corresponding tothe first screw hole 124. The second screw hole 144 is used to separateor remount the bonded abutment 120 and prosthetic appliance 140 from orto the fixture 110 rather than to fix the abutment 120 to the fixture110.

An outer surface 122 of the abutment 120 approximately corresponds to,but does not completely accord with, an inner surface 142 of theprosthetic appliance 140 in shape. That is to say, by providing anallowance space between the abutment 120 and the prosthetic appliance140, the prosthetic appliance 140 is passively fitted to the abutment120.

Dental cement 150 is interposed between the abutment 120 and theprosthetic appliance 140 so that the abutment 120 and the prostheticappliance 140 are bonded.

The method for treating the SCRP implant 100 will be explained belowreferring to the accompanying drawings.

Referring to FIG. 4 a, when the four fixtures 110 are implanted into analveolar bone, the fixtures 110 are not parallel to each other and areimplanted with inclination at certain angles. Therefore, the joiningprojections 112 formed on the upper surfaces of the fixtures 110 aredirected in to different directions from each other.

Referring to FIG. 4 b, each of abutments 120 a, 120 b, 120 c is fixed toeach of the fixtures 110. The abutments 120 a, 120 b, 120 c are fixed tothe fixtures 110 with the screws 130.

However, since the implanted directions of the fixtures 110 aredifferent from each other, the prosthetic appliance 140 beforeprocessing cannot be correctly fitted to the abutments. Therefore, eachof the abutments 120 a, 120 b, 120 c should be formed with asubstantially vertical stop. In order to form the vertical stop, thewall surface or margin of the abutments 120 can be partially cut orremoved.

Referring to FIG. 4 c, each of the abutments 120 a, 120 b, 120 c, 120 dis fixed to each of the four fixtures 110 and is formed in considerationof the implanted angle of each of the fixtures 110 and the entry angleof the prosthetic appliance 140.

Even in the oral cavity, the abutments 120 a, 120 b, 120 c, 120 d may bepartially modified with a hand drill at high or low speed.

Referring to FIG. 4 d, the fabricated prosthetic appliance 140 isprovided. The prosthetic appliance 140 is formed by casting a frameworkaccording to a general method, and the second screw holes 144 are formedalong with the framework. In order to prevent breakage of the material,a metal chimney may be formed up to an occlusal surface. However,depending on the circumstances, the metal cannot be also used around thesecond screw holes 144 (which is referred to as a metal free hole) froman aesthetic point of view. The framework of the prosthetic appliance140 is adjusted for the passive fit correspondingly to the abutments 120a, 120 b, 120 c, 120 d and is formed with inner surfaces 142 a, 142 b,142 c, 142 d, which are different from each other.

Referring to FIG. 4 e, the permanent cement 150 is interposed betweenthe prosthetic appliance 140 and the abutments 120 a, 120 b, 120 c, 120d so that the prosthetic appliance 140 and the abutments 120 a, 120 b,120 c, 120 d are bonded.

Before bonding the abutments 120 a, 120 b, 120 c, 120 d to theprosthetic appliance 140, the prosthetic appliance 140 may be subjectedto trial adaptation. When the prosthetic appliance 140 has beensubjected to the trial adaptation, as shown in the figures, theabutments 120 a, 120 b, 120 c, 120 d may be repositioned to the fixtures110 without the prosthetic appliance 140. Repositioning the abutments inthe oral cavity may be performed due to the existence of stickinggrooves of the abutments which accord with the shape of the joiningprojections of the fixtures.

This is one of the important features of the abutments. The reason isthat each of the abutments 120 a, 120 b, 120 c, 120 d has a differentform by deforming its upper structure in order to fabricate optimalprosthetic appliances. Therefore, each of the abutments 120 a, 120 b,120 c, 120 d should be fixed to the fixture at a precise position andangle. If the abutments are fixed at inaccurate angles due to rotation,the previously fabricated prosthetic appliance 140 becomesinappropriate.

As another method, all of the abutments 120 a, 120 b, 120 c, 120 d maybe fixed to the fixtures 110 at one time through the second screw holes144 by inserting all of the abutments into the prosthetic appliance 140.There may be an abutment that would not be fixed since the prostheticappliance 140 does not fit precisely. This problem can be solved bytighten the screw after separating only the prosthetic appliance 140 byloosening the screw and then repositioning the abutment that is notfixed to fit the sticking groove.

Tightening and loosening the screws 130 can be adjusted through secondscrew holes 144 a, 144 b, 144 c, 144 d. The prosthetic appliance 140rests on the abutments 120 a, 120 b, 120 c, 120 d without anyresistance, and the abutments 120 a, 120 b, 120 c, 120 d can be adjusteduntil the border fits completely.

After adjusting the fit between the abutments 120 and the prostheticappliance 140 by the trial adaptation of the prosthetic appliance 140,the first screw holes 124 of the abutments 120 are filled with gauze orcotton. The reason for using the supplementary filler such as the gauzeor cotton is that the first screw holes 124 are prevented from becomingclogged with the cement introduced into the first screw holes 124 whenbonding the abutments 120.

Then, after interposing the permanent cement 150 between the abutments120 and the prosthetic appliance 140, the abutments 120 and theprosthetic appliance 140 are bonded. Resin luting cement and the likemay be used as the permanent cement 150.

After a lapse of certain time, the permanent cement 150 hardens so thatthe abutments 120 and the prosthetic appliance 140 are bonded.

Referring to FIG. 4 f, after the abutments 120 and the prostheticappliance 140 are bonded, the supplementary filler with which the firstscrew holes 124 are filled is removed. Then, the abutments 120 a, 120 b,120 c, 120 d and prosthetic appliance 140 may be separated from thefixtures 110 by loosening all of the screws 130 through the first andthe second screw holes 124, 144. At this time, the abutments 120 a, 120b, 120 c, 120 d constitute a prosthesis portion by bonding them to theprosthetic appliance 140.

Contrary to the conventional cement retained prosthesis (CRP), evenafter bonding the abutments 120 and the prosthetic appliance 140, theprosthesis of the present invention can be separated. This is the reasonwhy all of the screws 130 can be removed through the second screw holes144 a, 144 b, 144 c, 144 d and a structural allowance space in theimproved abutments 120 is provided.

After separating the prosthesis portion, which is constituted by theabutments 120 a, 120 b, 120 c, 120 d and the prosthetic appliance 140,the remaining cement around a gingiva and the abutments 120 can beremoved and the fit can be precisely adjusted by polishing the border ofthe prosthetic appliance 140.

In final brief, the method for treating the SCRP implant is completed byinserting the prosthetic portion into the oral cavity, fixing theprosthetic portion to the fixture 110 with the screw 130, and closingthe second screw hole 144 a, 144 b, 144 c, 144 d by filling it withplastic or ceramic material.

Embodiment 2

FIG. 5 a is a sectional view of an SCRP implant according to Embodiment2 of the present invention, and FIG. 5 b is a sectional view forexplaining a separating process of the SCRP implant according toEmbodiment 2.

Referring to FIG. 5, the SCRP implant according to Embodiment 2comprises the fixture 110, an abutment 120, the screw 130 and theprosthetic appliance 160. The fixture 110, screw 130 and prostheticappliance 160 except the abutment 120 may refer to the explanations anddrawings of Embodiment 1, and repetitional contents may be omitted.

The fixture 110, the abutment 120 and the screw 130 except a prostheticappliance 160 may refer to the explanation and drawings of Embodiment 1,and repetitive description may be omitted.

The hexagonal cylindrical joining projection 112 is formed on the uppersurface of the fixture 110, in which a thread hole corresponding to thescrew 130 is formed along the centerline of the joining projection 112.The abutment 120 comprises the receiving portion for receiving thejoining projection 112 and the receiving portion is formed in ahexagonal cylindrical shape, which corresponds to the shape of thejoining projection 112. The first screw hole 124 is formed on the centerof the abutment 120 and the screw 130 is engaged with the fixture 110through the first screw hole 124.

The prosthetic appliance 160 is fabricated of a two-layered structure ofa metal framework 162 and a porcelain 164. The metal framework 162 isformed with a hole corresponding to the first screw hole 124, and theporcelain 164 is formed on the metal framework 162 in the form of atooth. Generally, although the conventional prosthetic appliance has astructure of a metal framework and a porcelain, the hole is not formedin the metal framework. Contrary to this, in the prosthetic appliance160 of the SCRP prosthesis according to the present embodiment, themetal framework 162 is formed with the hole. Since the layer of theporcelain 164 is formed on the metal framework 162 with the hole formed,immediately after treatment, since a portion 166P corresponding to thesecond screw hole is not exposed, an aesthetic appearance can beachieved, and foreign body sensation immediately after the treatment canbe considerably reduced.

Furthermore, a second screw hole 166 may be formed hereafter by using adelicate drill D, so that the screw 130 can be easily separated throughthe first and the second screw holes 124, 166. The treatment method ofthe present embodiment, which is a modification of the treatment methodof the SCRP prosthesis according to Embodiment 1, has the feature thatthe second screw hole 166 is formed hereafter.

By forming the second screw hole 166, the bonded abutment 120 andprosthetic appliance 140 can be easily separated from the fixture 110,and the abutment 120 and prosthetic appliance 140 can be also easilyremounted to the fixture 110.

The outer surface 122 of the abutment 120 approximately corresponds to,but does not completely accord with, the inner surface of the metalframework 162 in shape. That is to say, like the cement retainedprosthesis, by providing an allowance space between the abutment 120 andthe prosthetic appliance 160, the prosthetic appliance 160 can bepassively fitted to the abutment 120. At this time, the dental cement isinterposed between the abutment 120 and the prosthetic appliance 160, sothat the abutment 120 and the prosthetic appliance 160 are bonded.

FIG. 6 is a sectional view of a SCRP prosthesis according to anotherembodiment of the present invention, which is similar to Embodiment 2.

Referring to FIG. 6, the SCRP prosthesis according to the presentembodiment also comprises the fixture 110, the abutment 120, the screw130 and a prosthetic appliance 160-1.

The prosthetic appliance 160-1 is constituted by a porcelain 164-1without a metal framework. After the prosthetic appliance 160-1 of theSCRP prosthesis according to the present embodiment is bonded, since theportion corresponding to the second screw hole is not exposed, anaesthetic appearance can be achieved, and the foreign body sensationimmediately after the treatment can be considerably reduced.Furthermore, a second screw hole may be formed hereafter by using adelicate drill D, so that the screw 130 can be easily separated throughthe first and the second screw holes. The treating method of the presentembodiment, which is also modification of the treating method of theSCRP prosthesis according to Embodiment 1, has the feature that thesecond screw hole is formed hereafter.

Embodiment 3

FIG. 7 is a partial sectional view of an SCRP prosthesis for explainingthe example of using an abutment for the SCRP prosthesis according toEmbodiment 3 of the present invention; FIG. 8 is a bottom partiallycutaway perspective view of the abutment of FIG. 7; and FIG. 9 is abottom view of the abutment of FIG. 7. A prosthesis and an abutment 200shown in FIGS. 7 to 9 are constituted by an external connection method.Explanation regarding the fixture 110 and the screw 130 may refer to theexplanation and drawings of Embodiment 1, and repetitive description maybe omitted.

Referring to FIGS. 7 to 9, the prosthesis comprises the fixture 110, theabutment 200 and the screw 130.

The fixture 110 comprises a thread 114 formed on an outer surfacethereof and is implanted into the alveolar bone along the thread 114. Onthe upper surface of the fixture 110, the hexagonal cylindrical joiningprojection 112 is formed. A thread hole is formed along the axial lineof the joining projection 112 and the fixture 110, so that the threadhole is engaged with the thread of the screw 130.

The abutment 200 consists of an integrally formed abutment body 210,through which first screw holes 220, 225 are formed upward and downward.If diameters of the first screw holes 220, 225 are different form eachother to form a step, the head of the screw 130 is supported on thestep. The screw 130 is inserted into the abutment 200 through the firstscrew hole 220 with the larger diameter.

The lower portion of the abutment 200 is formed with a receiving portion230 for receiving the joining projection 112 of the fixture 110, whereinthe receiving portion 230 is divided into a sticking groove 240 and anallowance groove 250.

The sticking groove 240 provides a hexagonal cylindrical inner surface,the dimension of which is nearly equal to that of the joining projection112 (but including a tolerance), so that the sticking groove 240 isstuck to the upper end of the joining projection 112. The allowancegroove 250 is defined by a conical inclined surface, which is formedwith inclination from the lower end of the sticking groove 240, andprovides an allowance space to easily separate and remount the joiningprojection 112. The allowance groove 250 is extended in the form of atrumpet and may be fabricated by cutting the lower portion of aconventional hexagonal cement retained abutment into a conical shape.

The inclined surface of the allowance groove 250 is inclined at about 15degree with respect to an outer surface of the joining projection 112.According to the present invention, it is preferable that the angle ofthe inclined surface is about 2 to 45 degrees. If the angle is overabout 45 degrees, since a contact area between the border of the fixture110 and the abutment 200 is too small, stability of the abutment 200 isdeteriorated.

Furthermore, when the depth of the sticking groove 240 is belowtwo-thirds of that of the receiving portion 230, the abutment 200 can bestably mounted to the fixture 110. As the sticking groove 240 becomesdeeper, it becomes more difficult to mount and separate the abutment200. If the sticking groove 240 is too shallow, the joining projection112 and the sticking groove 240 run idle with respect to each other, sothat the abutment 200 can be easily rotated. Furthermore, it may beinfluenced by the tolerance between the joining projection 112 and thesticking groove 240. Therefore, the depth of the sticking groove 240should be properly maintained. According to the present invention, it isdesirable that the depth of the sticking groove 240 is about 10˜80% of adepth of the receiving portion 230. In the present embodiment, adiameter of the border of the fixture 110 is about 4.1 mm; the depth ofthe receiving portion is about 0.7˜1.0 mm; and the depth of the stickinggroove 240 is about 0.1˜0.6 mm. According to another constitution of thefixture, a diameter of the border may be variously adjusted to about 5.0mm, 5.5 mm, 6.0 mm and the like, so that the dimensions of the receivingportion and the sticking groove can be also variously changed.

FIG. 10 is a front view for explaining engagement between the abutmentand the fixture according to Embodiment 3.

Referring to FIG. 10, when the prosthetic appliance 140 and abutment 200are separated from the fixture 110, the upper end of the joiningprojection 112 frees itself from the sticking groove 240 so that anallowance space S is generated around the joining projection 112. Due tosuch an allowance space S, the receiving portion 230 of the abutment 200can be easily separated from the fixture 110.

Furthermore, as the joining projection 112 approaches the receivingportion 230 of the abutment 200 even when the abutment 200 is remounted,the joining projection 112 is directly inserted into and then fixed tothe sticking groove 240 of the receiving portion 230. However, in mostcases, a portion of the joining projection 112 first contacts theinclined surface of the allowance groove 250. The joining projection 112is guided along the inclined surface to the sticking groove 240, and theabutment 200 can be also mounted to the fixture 110.

That is to say, due to the allowance space S, the abutment 200 can beeasily separated and mounted. Such a feature is obviously shown in thecase of the treatment with the two or more prostheses integrally formed.

FIG. 11 is a partial sectional view for explaining the example of usingthe abutment according to Embodiment 3, and shows an example of thetreatment with the two prosthetic appliances integrally formed.

Referring to FIG. 11, the two fixtures 110 are implanted and fixed intothe alveolar bone (not shown), and the fixtures 110 are not parallel toeach other and are inclined at certain angles. In the mean time, theprosthetic appliance 140 corresponding to two teeth is formed as apiece, and the abutments 200 are bonded to lower portions of theprosthetic appliance 140.

In order to separate the integrally bonded prosthetic appliance 140 andabutments 200 from the fixtures 110, the screws are removed throughsecond screw holes 144 a, 144 b, and the prosthetic appliance 140 andabutments 200 are pulled at once.

As shown in the figures, the screws are removed, the allowance space Saround the joining projection 112 is provided by slight movement of theabutments 200, and due to the allowance space S, the prostheticappliance 140 and abutments 200 are easily separated from the fixture.To the contrary, the integrally formed prosthetic appliance 140 andabutments 200 are easily engaged to the fixture 110.

The conventional hexagonal abutment is advantageously repositioned atthe same position of the fixture. However, under the same condition asin FIG. 11, interference of an inlet end of the receiving portion withthe joining projection 112 of the fixture prevents the joiningprojection 112 from being separated. Thus, the joining projection 112cannot be easily separated from the fixture 110. Of course, if theabutments and the fixtures are mutually twisted, the abutments that facein different directions from each other cannot be easily fixed to thefixtures.

Compared with this, the abutment according to the present embodiment canbe easily repositioned and, as shown in FIG. 4 f, is usefully applied toseparating the bonded abutment and prosthetic appliance from thefixture.

Embodiment 4

FIG. 12 is a bottom partially cutaway perspective view of an abutmentaccording to Embodiment 4 of the present invention, and FIG. 13 is afront view for explaining the engagement between the fixture and theabutment according to Embodiment 4. An abutment 201 shown in FIGS. 12and 13 features a cylindrical allowance groove 260. The otherconstitutions and functions are substantially the same as those of theprevious embodiments. Therefore, the explanation of the presentembodiment may refer to the explanations and drawings of the previousembodiments, and repetitive description may be omitted.

Referring to FIGS. 12 and 13, a prosthesis comprises the fixture 110,the abutment 201 and the screw 130, wherein the abutment 201 is fixed tothe fixture 110 by the screw 130 that is inserted through the firstscrew hole 220.

The abutment 201 consists of the integrally formed abutment body 210,through which the first screw holes 220, 225 are formed upward anddownward.

A lower portion of the abutment 201 is formed with a receiving portion231 for receiving the joining projection 112 of the fixture 110, whereinthe receiving portion 231 is divided into the sticking groove 240 andthe allowance groove 260. The sticking groove 240 provides a hexagonalcylindrical inner surface corresponding to the joining projection 112,and is stuck to the upper end of the joining projection 112. Theallowance groove 260 is formed in a step shape from the lower end of thesticking groove 240, and provides the circular cylindrical space with adimension larger than that of the sticking groove 240. Therefore, theallowance groove 260 provides the allowance space S, which causes thejoining projection 112 to be easily separated and remounted.

Compared with the inclined allowance groove 250 of Embodiment 3, thecircular cylindrical allowance groove 260 may have almost the sameeffects.

Even in the present embodiment, when the abutment 201 is separated fromthe fixture 110, the upper end of the joining projection 112 freesitself from the sticking groove 240, and the allowance space S is formedaround the joining projection 112. Due to the allowance space S, thereceiving portion 231 of the abutment 201 can be easily separated fromthe fixture 110. The abutment 201 is easily remounted to the fixture110.

Embodiment 5

FIG. 14 is a bottom partially cutaway perspective view of an abutmentaccording to Embodiment 5 of the present invention. An abutment 202shown in FIG. 14 has a feature of a complex allowance groove 255 intowhich the inclined allowance space of Embodiment 3 and the step shapedallowance space of Embodiment 4 are effectively combined. The otherconstitutions and functions are substantially the same as those of theprevious embodiments. Therefore, the explanation of the presentembodiment may refer to the explanations and drawings of the previousembodiments, and repetitional contents may be omitted.

Referring to FIG. 14, a prosthesis comprises the fixture, the abutment202 and the screw, wherein the abutment 202 is fixed to the fixture 110by the screw that is inserted through the first screw hole 220.

The abutment 202 consists of the integrally formed abutment body 210,through which the first screw holes 220, 225 are formed upward anddownward.

A lower portion of the abutment 202 is formed with a receiving portion232 for receiving the joining projection of the fixture, wherein thereceiving portion 232 is divided into the sticking groove 240 and theallowance groove 255. The sticking groove 240 provides a hexagonalcylindrical inner surface corresponding to the joining projection, andis stuck to the upper end of the joining projection.

The allowance groove 255 comprises partially an inclined allowance spaceformed in a conical shape from the lower end of the sticking groove 240and comprises a step shaped allowance space formed in a step shape fromthe lower end of the inclined allowance space. The step shaped allowancespace is larger than the inclined allowance space in a dimension and isformed in a circular cylindrical shape. In order to fabricate theallowance groove 255 according to the present embodiment, by forming aconical allowance groove as Embodiment 3 and then forming a circularcylindrical allowance groove as Embodiment 4, the allowance groove 255is formed.

If an allowance groove is formed only with inclination as the allowancegroove 250 of Embodiment 3, in order to form an allowance groove with asufficient space, since the sticking groove 240 tends to be too low, anunstable engagement between the abutment and the fixture often occurs.However, by forming an upper portion of the allowance groove 255 in aninclination shape and the lower portion thereof in a step shape as inthe present embodiment, the sticking groove 240 can be formed to be highand stable engagement between the abutment and the fixture can beachieved.

Even in the present embodiment, when the abutment 202 is separated fromthe fixture, the upper end of the joining projection frees itself fromthe sticking groove 240, and the allowance space is formed around thejoining projection. Due to the allowance space, the receiving portion232 of the abutment 202 can be easily separated from the fixture.

Embodiment 6

FIG. 15 is a bottom partially cutaway perspective view of an abutmentaccording to Embodiment 6 of the present invention. An abutment 203shown in FIG. 15 has a feature of a receiving portion 233, which isformed with inclination as the allowance groove 250 of Embodiment 3 andcomprises concave portions 272 at the connecting portion of an allowancegroove 270 and the sticking groove 240. The other constitutions andfunctions are substantially the same as those of the previousembodiments. Therefore, the explanation of the present embodiment mayrefer to the explanations and drawings of the previous embodiments, andrepetitive description may be omitted.

Referring to FIG. 15, a prosthesis comprises the fixture, the abutment203 and the screw, wherein the abutment 203 is fixed to the fixture bythe screw that is inserted through the first screw hole 220.

The abutment 203 consists of the integrally formed abutment body 210,through which the first screw holes 220, 225 are formed upward anddownward.

A lower portion of the abutment 203 is formed with the receiving portion233 for receiving the hexagonal joining projection of the fixture,wherein the receiving portion 233 is divided into the sticking groove240 and the allowance groove 270. The sticking groove 240 provides thehexagonal cylindrical inner surface corresponding to the joiningprojection, and is stuck to the upper end of the joining projection.

The allowance groove 270 comprises an inclined allowance space formedwith inclination from the lower end of the sticking groove 240 asEmbodiment 3, and the joining projection can be introduced into orseparated from the receiving portion 233 along the inclined allowancespace. Furthermore, the concave portions 272 are partially concavelyformed at portions adjacent to the inlet of the receiving portion 233 inthe connecting portion of the sticking groove 240 and the allowancegroove 270, that is to say, at portions where the angled corners of thesticking groove 240 meet the inclined surface of the allowance groove270. At the portions where the concave portions 272 are formed, thesticking groove 240 is extended toward the inlet of the receivingportion 233. If the sticking groove 240 is formed to be high, thesticking groove and the joining projection interfere with each other, sothat it is possible to prevent the engaging and separation of thefixture. Therefore, the concave portions 272 are partially concaved sothat the joining projection can be smoothly moved.

Furthermore, if an allowance groove is formed with only an inclinationas the allowance groove 250 of Embodiment 3, in order to form anallowance groove with a sufficient space, since the sticking groove 240tends to be low, unstable engagement between the abutment and thefixture often occurs. However, by forming the allowance groove 270 withinclination and forming the concave portions 272 as in the presentinvention, the sticking groove 240 can be formed to be high and thestable engagement between the abutment and the fixture can be achieved.

Even in the present embodiment, when the abutment 203 is separated fromthe fixture, the upper end of the joining projection frees itself fromthe sticking groove 240, and the allowance space is formed around thejoining projection. Due to the allowance space, the receiving portion233 of the abutment 203 can be easily separated from the fixture.

INDUSTRIAL APPLICABILITY

According to the present invention, the methods for treating the SCRPimplant adopt the advantages of both of the screw retained type and thecement retained type and solve the disadvantages of both types, so thatmost of the conditions, which an implant prosthesis requires, aresatisfied.

That is to say, with the present invention, the passive fit between theimplant and the prosthetic appliance can be easily achieved; sincetightening the screw can be properly adjusted, the screw does not oftencome loose, and can be retightened without damage to the prostheticappliance when the screw is loosened; the prosthetic appliance is easilyseparated and mounted compared with the cement retained type; missingpotential of the prosthetic appliance is decreased since the permanentcement can be used without a burden; and it is possible to be applied ina case of short intermaxillary distance. Furthermore, cement ofsubgingival can be easily removed; the border of the prostheticappliance can be polished; the manual operational processes and clinicalprocedures are simple; time and cost can be considerably saved; due tofewer limitations, selection of kinds of metals for the prostheticappliance is free; it is very advantageous in an instant treatment forthe implant; it is possible to be applied to most cases; the prostheticappliance can be separated without damage and bonded again even when thecement in one of the abutments in plural implant prostheses is weak orbad; and since a large force is not applied to the implant though thescrew is strongly tightened, the screw can be tightened by the requiredtorque even in an implant of weak ossein.

Furthermore, in the abutment according to the present invention, thesticking groove and the allowance groove are formed in the receivingportion, which is engaged to the fixture. Therefore, the abutment can berepositioned in the fixture by the sticking groove; and due to theallowance groove, even after the abutment and the prosthetic applianceare bonded, they can be easily separated from and remounted to thefixture. Especially, in the case that two or more abutments areintegrally fixed to a prosthetic appliance, the allowance groovesprovide the allowance spaces in order for the joining projections of thefixtures to be easily separated, and the sticking grooves guide theabutments to be positioned in the fixtures correctly.

Furthermore, since the prosthetic appliance and abutment can be easilyseparated from and remounted to the fixture, when the implant is brokenor the screw is loosened, the implant can be easily repaired, mended andreplaced.

Furthermore, since the abutment according to the present invention maybe embodied on the basis of the structure of the most conventionalabutment, the present invention is very economical.

As described above, though the present invention is explained referringto the preferable embodiments, it is understood by one skilled in theart that the present invention can be modified or revised withoutdeparting from the spirit or scope of the present invention described inthe following claims.

1. A method for treating a screw-cement retained prosthesis, comprisingthe steps of: repositioning and engaging an abutment including a firstscrew hole to a fixture using a screw; providing a prosthetic appliancehaving a second screw hole formed correspondingly to the first screwhole; and bonding the prosthetic appliance and the abutment byinterposing dental cement between the abutment and the prostheticappliance.
 2. The method as claimed in claim 1, further comprisingremoving the screw through the second screw hole; separating the bondedprosthetic appliance and abutment from the fixture; removing theremaining cement; and polishing a border of the prosthetic appliance. 3.The method as claimed in claim 1, wherein a receiving portion is formedon the lower end of the abutment corresponding to a joining projectionformed on an upper end of the fixture, and the receiving portion isdivided into a sticking groove stuck to the upper end of the joiningprojection and an allowance groove providing an allowance space for thejoining projection easily to move in the receiving portion, so that theprosthetic appliance can be easily separated from or stuck to theabutment by the allowance groove.
 4. The method as claimed in claim 3,wherein the joining projection and the sticking groove are non-circular.5. The method as claimed in claim 3, wherein the allowance groove isformed with inclination from a lower end of the sticking groove so thatan allowance space, which is needed to separate and stick the joiningprojection, is provided and an entry of the joining projection isguided.
 6. The method as claimed in claim 3, wherein the allowancegroove is formed in a step shape from the lower end of the stickinggroove, so that a circular cylindrical or polygonal cylindricalallowance space with a dimension larger than that of the sticking grooveis provided.
 7. The method as claimed in claim 1, wherein each of aplurality of the abutments is engaged with each of the fixtures that areimplanted at predetermined intervals, and the prosthetic appliance isbonded to the abutments at once.
 8. A method for treating a screw-cementretained prosthesis, comprising the steps of: providing an implantwherein an abutment including a first screw hole is engaged with afixture by a screw and a prosthetic appliance is bonded to the abutment;forming a second screw hole, which corresponds to the first screw hole,on the prosthetic appliance; and separating the prosthetic appliance andabutment from the fixture by loosening the screw through the first andthe second screw holes.
 9. The method as claimed in claim 8, wherein theprosthetic appliance comprises a metal framework, which is formed at alower portion thereof and directly receives the abutment, and aporcelain, which is formed on the metal framework, and the metalframework comprises a hole corresponding to the first screw hole inorder to form the second screw hole.
 10. The method as claimed in claim8, wherein the prosthetic appliance is constituted by a porcelain. 11.An abutment for a screw-cement retained prosthesis, comprising: a screwhole formed upward and downward through an abutment body; and areceiving portion for receiving a joining projection formed on an upperend of a fixture; wherein the receiving portion comprises a stickinggroove stuck to an upper end of the joining projection and an allowancegroove providing an allowance space, which causes the joining projectionto be easily separated from and joined to the sticking groove.
 12. Theabutment as claimed in claim 11, wherein the sticking groove isnon-circular correspondingly to a shape of the upper end of the joiningprojection.
 13. The abutment as claimed in claim 11, wherein thesticking groove is circular correspondingly to a shape of the upper endof the joining projection.
 14. The abutment as claimed in claim 11,wherein a depth of the sticking groove is between 10%˜80% of the depthof the receiving portion.
 15. The abutment as claimed in claim 11,wherein the allowance groove is formed with inclination from the lowerend of the sticking groove so that an entry of the joining projection isguided.
 16. The abutment as claimed in claim 15, wherein the inclinedinner surface of the allowance groove is formed in a conical shape. 17.The abutment as claimed in claim 15, wherein the inclined inner surfaceof the allowance groove is formed with inclination of from 2 to 45degrees.
 18. The abutment as claimed in claim 11, wherein the allowancegroove is formed in a step shape from the lower end of the stickinggroove so that a circular cylindrical or polygonal cylindrical allowancespace with a dimension larger than that of the sticking groove isprovided.
 19. The abutment as claimed in claim 11, wherein the allowancegroove comprises an inclined allowance space for guiding an entry of thejoining projection, formed with inclination from the lower end of thesticking groove, and a step-shaped allowance space shaped of circularcylindrical or polygonal pillar with a dimension larger than that of theinclined allowance groove, formed into a step shape from the lower endof the inclined allowance space.
 20. The abutment as claimed in claim11, wherein the sticking groove is formed in a polygonal cylindricalshape corresponding to the upper end of the joining projection; theallowance groove is formed with inclination from the lower end of thesticking groove to guide an entry of the joining projection; andportions adjacent to an inlet of the receiving portion in a connectingportion of the sticking groove and the allowance groove are partiallyconcaved to cause the joining projection to be smoothly moved.